sin69°-sin3°+sin39°-sin33°(sin69+sin39º)-(sin33º+sin3º) (分组 ）=2sin[(69º+39º)/2]cos[(69º-39º)/2]-2sin[(33º+3º)/2]cos[(33º-3º)/2] 是怎么转换的?

来源：学生作业学帮网 编辑：学帮网 时间：2024/05/04 00:33:26

sin69°-sin3°+sin39°-sin33°
(sin69+sin39º)-(sin33º+sin3º) (分组 ）
=2sin[(69º+39º)/2]cos[(69º-39º)/2]-2sin[(33º+3º)/2]cos[(33º-3º)/2] 是怎么转换的?

sin(a+b)=sinacosb+sinbcosa
sin(a-b)=sinacosb-sinbcosa
相加得到[sin(a-b)+sin(a+b)]=2sinacosb
相减得到[sin(a+b)-sin(a-b)]=2sinbcosa
由此推算出来的
sinx+siny=2sin[(x+y)/2]cos[(x-y)/2]

用了和差化简公式

sin69°-sin3°+sin39°-sin33°(sin69+sin39º)-(sin33º+sin3º) (分组 ）=2sin[(69º+39º)/2]cos[(69º-39º)/2]-2sin[(33º+3º)/2]cos[(33º-3º)/2] 是怎么转换的? sin69度－sin3度＋sin39度－sin33度 sin69-sin3+sin39-sin33解题过程和详细的文字讲解 (sin39° -sin21°)/(cos39°-cos21°) sin21°cos39°+cos21°sin39°= cos39°cos9°+sin39°sin9°= cos24°cos69°-sin24°sin69°等于多少 sin21°cos81°-sin69°cos9° 求值：sin21°cos81°-sin69°cos9° sin21°cos81°+cos189°sin69°化简 (sin24°cos6°-sin66°sin6°)/(sin21°cos39°-cos21°sin39°) sin39°-sin30°cos9°/cos39°-cos30°cos9° 求sin39°-sin21°/cos39°-cos21°的值急需过程,谢谢! 设cos31°=α,则sin39°+tan149°= sin21°cos81°+sin69°cos9°化简要详解 sin21°cos189°-sin69°sin9°的值为 sin21°cos189°-sin69°sin9°的值为 解斜三角形应用某人在山外一点测得山顶的仰角为42°,退后30M测得山顶为39°,则山高为（sin42=0.6691,sin39=0.6293,sin3=0.0523)A180m B241M C241M D266M